Pressure operated switch



F. R. COLGAN, JR 2,560,276 PRESSURE OPERATED SWITCH July 10, 1951 Filed May 12, 1947 3 Sheets-Sheet l 2/ LEF% FRo-; RIGHT LE FT?) REAR @)\R4GHT y 1951 F. R. COLGAN, JR 2,550,276

PRESSURE OPERATED SWITCH Filed May 12, 1947 3 Sheets-Sheet 2 y 1951 F. R. COLGAN, JR 2,560,276

PRESSURE QPERATED SWITCH Filed May 12, 1947 3 Sheets-Sheet 5 Patented July 10, .1951

UNITED STATES PATEN OFFICE PRESSURE OPERATED SWITCH Fred R.:Colgan,.;lr., Los Angeles Calif. Application Maylz, 1947,-Serial.N0. 747,530 Cla'ims. (Cl. 200-58) This invention relates to electric signalling or alarm systems .and .in particular to such .systems for automatically notifying the operator of a vehicle equipped with pneumatic tires whenever the inflation .pressure of ,any one of the tires .drops .below a normal predetermined value considered .safe for driving.

An .obj'ect of the invention is to provide .an improved pressure controlled switch for use in ofeach wheelof the vehicle in pressure relation with the inner tube. The new switch maybe manufacturedat very low cost .as compared with other types of switches that have been .developed heretofore for such application; it features contacts sealed against ingress of dirt, oil and moisture, .has a minimum number .of moving parts, is compact in structure and well protected against damage when installed and is most reliable in operation. Furthermore the switch has the additional advantage in that wheels already in use can be modified at but little expense to permit .installation of the switch. A more specific object is to provide :a switch for tire pressure signalling systems comprising relatively movable contact members carried within and supported by a molded body of resilientmaterial such as rubber, the contact members being actuated relative to each other by deformation of the body member in accordance with variation in pneumatic pressure of the inner tube of .the tire. Another object is to provide a switch of the class described in which the contacts may be easily adjusted for operation .-at different pneumatic pressures.

The foregoing and other objects and advantages to be derived from the invention will become more apparent from the following detailed description of several preferred forms of the switch and the accompanying drawings.

In the drawings Fig. 1 is adiagram-matic view of a tire pressure signalling system in which each .of the four wheels of the vehicle is provided with .a switch embodying the invention, one of the wheels being :shown partly :insection to shown installation idetails;

Fig. .2 is a plan view of one form-of the switch as installed in the rim -portion of the wheel;

Fig. 3 is .a verticalcentral section taken on .line 3-3 .of 2;

Fig. 4 is also .a vertical central section taken on line 3--.3 .of Fig- .2; but with the adjusting screw in va -.diiferent position to illustrate the manner in which the switch contacts are adjusted for operation .at a selected tire inflation pressure;

Fig. 5 is a vertical section taken on line '5--5 of Fig. ,2 showing the positions of the switch contacts when the molded rubber body member is free from pressure;

Fig. 6 shows the same section as Fig. 5 but with the molded .rubiber body subjected to the pressure of the inner tube causing separation of the switch contacts;

.Fig. 7 is a perspective view showing the construction of the contact vmembers of the switch illustrated in Fig. .2;

Figs. '8 and 9 areplanand vertical central sections respectively of -a modified embodiment of switch incorporating the invention; and

Figs. 10 and 1.1 arealso-plan-and vertical central sections respectivelyof still another embodiment of switch constructed in accordance with the invention.

Referring .now to the drawings and in particular to Figs. .2-7, the switch or actuator unit S for use in the signalling system shown in Fig. 1 for indicating a low-pressure condition in the vehicle tires is, seen to be comprised of a cylindrical ,body I of resilient material such as rubber having upper and lower end flanges Ia, lb .by which the body 5 is supported within an opening .2 in the .rim .3 of the vehicle Wheel :3. The opening 2:1'n the .rim Sis so correlated to the diameter of the body I that the latter will be held snugly in place on the rim after it has been installed by deforming the lower flange it to pass it through the rim opening. The axial length of the 'body I between the upper and lower flanges I a, H) is made substantially equal to the thickness-of the rims so that these flanges will lie substantially flat against the upper and lower surfaces of the rim adjacent the rim opening 2 notwithstanding the slight curvature of the rim in the rim plane.

The contacts of the switch S which are imbedded in the rubber body I include a substantially annular metallic disc 6 of conductive material, the outer diameter of which is greater than the diameter of opening .2 through the rim so that the surface of disc 5 overlies the marginal surface portions .of the rim adjacent the rim opening 2. The disc contact 6 thus stilfens the inner .flange laof the rubber body I, i. e. the side facing the tire and tube, and serves to prevent the body .I from beingblown out through the .rim .hole 2 .under excessive pneumatic pressure in the inner tube.

Disc 6 is provided with a pair of inwardly extending ears l which are adapted to be engaged by the movable contact member 8 of the switch. Disc 6 is also provided with a downwardly turned tongue 9, the lower portion of which is bent to lie horizontally and threaded to receive an adjusting screw H). The inner end of screw I is provided with a serrated head H and the outer end of the screw which projects outwardly from the body i is slotted at i2 to receive a screw driver. More will be said later about the adjusting screw it and its function for setting the switch contacts for operation at a selected tire pressure.

The movable contact member 8, as seen clearly in Fig. '7, and which like contact member 6 is also imbedded within the rubber body I, is stamped from flat, electrically conductive, metal plate and thereafter bent to provide a central plate section I l, a tongue 15 and a pair of contact arms 16 which are adapted to move into and out of engagement with the ears ,l of the stationary contact member 6. As seen in Fig. 3, tongue it passes beneath the annular contact member t and rests in good contact with the outer surface of rim 3.

Prior to molding the rubber body I, the adjusting screw 10, the ear portions 1 of contact member 6 and the outer ends of contact arms iii are first coated with a lubricant such as grease to prevent their adherence to the rubber. Screw i0 is then threaded into the tongue 9 until the head ll contacts the latter. A lead wire ll is then soldered to the tongue on ring contact 6. The assembly of the ring contact and screw is then positioned in the mold cavity, being supported from the lower end of a screw it which is inserted into a close-fitting hole in the bottom I1 is led out through another small hole in the mold. The movable contact member 8 is then placed in the mold with the upper edges of the two contact arms lfe in touching engagement with the ears 1 of the ring contact 65. It can be held in this osition by the tongue it which can be inserted in a close-fitting f opening in the side of the mold. The mold is then closed and the rubber introduced in accordance with standard molding practice.

After molding, the only parts protruding from the rubber body I will be the lower portion of the adjusting screw H), wire H and the end of the tongue i that was inserted in the mold wall for supporting the movable contact member 3 in position while the rubber body I was being molded. This end can now be cut off so that it lies substantially flush with the body l. The switch unit is now complete and can be installed in the wheel rim 3 by forcing the lower flange lb of the rubber body through the rim opening 2.

Following installation of a switch unit S on the rim of each wheel, the tires I8 and tubes is are placed on the rims and inflated to the preselected pressure chosen as the normal pressure, and below which it is desired that a signal shall be transmitted to the operator of the vehicle.

Referring now to Fig. 1, the signalling system for the vehicle includes a housing 2| suitable for mounting on or near the instrument panel of the vehicle and which contains an indicating element such as lamp 22 for each one of the wheels. One side of the filament in each of the lamps 22 is connected to the positive terminal of the battery 23, the negative terminal of which is grounded to the vehicle frame in fall below the normal value,

, serve to lockthe screw l0 against any 4 accordance with the usual practice followed in the automotive industry. The leads I! from the stationary contact members 6 of the several switch units S extend to a collector ring 2 3 set flush with the surface of an annular disc 25 of insulating material which is supported within the brake housing 26 of each wheel, and a lead 21 from the other side of the filament of each of the lamps 22 extends to a brush 23 on each wheel that is supported for sliding engagement with the collector rings 24. The tongue portion it of the movable contact member 8 of each switch unit S rests in good contact with the associated rim 3, and since the latter are connected through the axles to the frame of the vehicle, it will be obvious that each of the movable contacts 8 is also at ground potential. Thus each of the signal lamps 22 will be lighted from battery 23 when the contact members 6 and 8 of its associated switch unit S are closed, but will be extinguished upon separation of the switch contacts.

The pressure exerted by the inner tube [9 against the upper flange la of the switch body i will then force the contact arms l6 downwardly as shown in Fig. 6 to disengage them from the ears I of the ring member 6. Although the latter also moves downward under the applied inner tube pressure, its displacement will be much less than that of the contact arm end of member 8 since the latter is mounted as a cantilever and hence bends considerably about the tongued supporting end i5 under the comparatively large amount of force applied by the inner tube to the relatively large area central plate section 14. The adjusting screw it is now turned with a screw driver to move the screw head ll away from the tongue 9 and thereby apply pressure upwardly upon an internal portion of the body I as shown in Fig. 4 over an area located generally between the contact arms 16, which pressure is of course opposite in direction to the pressure applied downwardly against resilient body I by the air pressure in the tube 19. Screw ID on each switch unit is moved upwardly until the resulting force applied upwardly just exceeds the downward force resulting from the air pressure in the inner tube l9. At this point, the contact arms N5 of the switch will now move upwardly to reengage the ears 1 on the stationary contact member 6 and hence close the corresponding circuit between battery 23 and the related signal lamp 22 causing the latter to light up. The adjusting screw it is now backed off slightly until the downward force applied to the resilient body I by inner tube l9 slightly exceeds the upward force applied by screw l0 whereupon the contact members 6, 8 of the switch unit S will separate and extinguish the lamp 22. This is the normal op-' eratin condition for the indicating system and so long as all the lamps remain unlighted, the operator will know that the air pressure in the tires is not less than the normal value preselected by the adjustment of the screws Hi. However, should the air pressure in any of the tires the force applied downwardly on the resilient body I will become less than the upward force to which the body l is stressed by the adjusting screw 10, with the result that the contact members 6 and 8 of the switch affected will close and light up the corresponding signal lamp 22 to call this fact to the attention of the operator. The serrations on screw head H bearing against the rubber body I rotation from its adjusted position that might result from vibration, etc.

A modified construction of the switch unit in which the switch contacts are maintained slightly separated by a strain in the resilient body when the tire pressure is normal but which close upon a drop in tire pressure is shown in Figs. 8 and 9. Here the resilient body 30 of switch unit S is also seen to be a short cylinder that can be fitted snugly within the opening 2 in rim 3, and is provided with top and bottom flanges 30a, 30b. The

nular surface portion of glisc 3! lies beneath flange 30a and seats firmly against the upper surface of rim 3 to establish a good electrical contact with the rim which is grounded to the frame of the vehicle. The movable contact member is comprised of The switch units S shown in Figs. 8 and 9 operates in accordance the switch include a metallic strip 38 molded centrally within the resilient body 3'! in a substantially vertical lower end of strip 38 being angle from horizontal, and

The lower end of the screw 39 is slotted and protrudes slightly out of the bottom of the resilient body 3? so as to permit adjustment, and the upper end of the screw terminates at the surface the flange 31b so as engagement with the edge of the rim 3 to break the circuit between the battery 23 and the corin the lamp housing 2|.

now remain unlighted so long as the tire-pressure stays at the preselected level. However, should the air pressure in any of the four tires decrease below the preselected normal the upper end of the contact screw 39 to touch the edge of the rim opening thereby completing the circuit between the battery 23 and the associated signal lamp 22 to indicate this condition to the operator of the vehicle.

In conclusion, it will be appreciated that the switch constructions described require but a simply designed working parts which when considered with the relatively inexpensive method of assembly by molding makes it possible to produce the low overall manufacturing cost.

tacts to keep out dirt, oil and moisture thereby assuring trouble-free operation. Furthermore it will be understood that while in accordance with I claim: 1. A switch through the rim for mounting in an opening of a vehicle wheel for actuation change in tire inflation opening.

2. A switch as defined in claim 1 wherein a part of one of said'contact members lies in contact with the rim.

3. A switch as defined in claim 1 wherein the contact pressure of the tire, and the other contact member is movable with the deformed portion of the resilient body to control an electrical circuit established between the two contact members.

4. A switch for mounting in the rim of a vehicle wheel for actuation in response to a change in tire inflation pressure, said switch comprising; a body member of resilient insulating material insertable through an opening in the rim and subject to the tire pressure, upper and lower end flanges on said body member engaging the upper and lower rim surfaces; a first contact member including an annular portion imbedded in the upper flange portion of said resilient body member, the inner diameter of said annular portion being at least equal to the diameter of the rim opening, spaced contact cars, a depending tongue with a horizontal offset and a headed vertical adjustment screw threaded through the horizontal ofiset of the tongue and located below and intermediate the contact ears; a second contact member imbedded in said resilient body member including a support tongue extending beneath the upper flange on said resilient body member for engagement with the upper surface of the rim, a central plate portion and outer spaced contact arms for engagement with the contact ears of said first contact member, the contact arms of said second contact being displaced relative to the contact ears of said first contact member upon a change in deformation of said resilient body member in response to a change in tire inflation pressure to control an electrical circuit established' between said first and second contact members.

5; A switch as defined in claim 1 wherein the contact'member including the annular portion also includes a diametral contact portion imbedded in the body member and bridging said annular portion, said annular portion being disposed in contact with the rim surface beneath the upper flange on said body member to render the contact member substantially stationary upon deformation of said resilient body member in response to the inflation pressure of the tire, and wherein the other of said contact members is comprised of a conductive element imbedded in said body member and an adjustable conductive screw threaded through said conductive element for engagement with the diametral contact portion of the other contact member.

FRED R. COLGAN, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 10,791 Kells, Jr Dec. 21, 1886 1,298,420 Tharp Mar. 25, 1919 1,769,427 Garside July 1, 1930 2,244,933 Armstrong June 10, 1941 2,343,060 Horning Feb. 29, 1944 2,367,441 Schwinn Jan. 16, 1945 

